Windows 3.1 HIMEM.SYS and Windows 3.0

• Microsoft Windows operating system versions 3.0, 3.0a, 3.1, 3.11

SUMMARY

Using the Microsoft Windows 3.1 HIMEM.SYS extended memory manager on an EISA system with more than 16 megabytes (MB) of memory can cause Windows version 3.0 to fail.

MORE INFORMATION

Windows 3.0 standard and enhanced modes rely on the HIMEM.SYS driver to "screen out" memory on the machine above 16 MB. Windows 3.0 standard and enhanced modes do not work well with memory above 16 MB, and Windows 3.0 does not function correctly if it is allowed to "see" this memory. Failure to screen this memory can result in reboots, general protection (GP) faults, failures to start, or data corruption.

In some cases, Windows 3.0 enhanced mode works correctly because the WIN386.EXE file from Windows 3.0 does some screening of its own.

The greater-than 16 MB memory screening is disabled in the HIMEM.SYS driver included with Windows 3.1. Windows 3.1 standard and enhanced modes do not need this screening because both modes fully support more than 16 MB of memory.

If it is necessary to have both Windows 3.0 and Windows 3.1 running on your machine, you should replace the automatically installed Windows 3.1 HIMEM.SYS driver with the Windows 3.0 HIMEM.SYS. Windows 3.1 standard and enhanced modes work correctly with the 3.0 version of the driver. However, remember that the HIMEM.SYS driver included with Windows 3.0 is limited to 16 MB of memory.